When nonporous substrates are relatively cool and are then exposed to a warmer moist atmosphere, the cooled surface has a tendency to become fogged. The accumulation of fog on the surface may be objectionable for several reasons. If the surface of the material is intended to be transparent, such as an automobile windshield or glass lenses or mirrors, such as those in bathrooms, the fogging can become a problem and often hazardous.
Several compositions have been suggested for applying to nonporous surfaces to prevent fog formation. Compositions which have been described as antifogging agents are those disclosed in U. S. Pat. No. 3,337,351 to Morehouse, which consists of aqueous or water-soluble organic liquid solutions of organosiloxane-oxyalkylene block copolymers.
Other water-repellent compositions which have been described for treating nonporous substrates are those disclosed in U. S. Pat. No. 3,244,541 to Fain et al and U. S. Pat. No. 3,579,540 to Ohlhausen. Fain, for example, discloses a waterrepellent composition containing a solution of an organic or inorganic acid and an alkylalkoxysilane, while Ohlhausen discloses a water-repellent composition containing an alkylpolysiloxane, a mineral acid and an alcohol solvent.
One of the objections to using these water-repellent compositions as antifog compositions is that they are not transparent when diluted with water. Another objection to these water repellent compositions is that they separate into two phases when diluted with water. In addition, these water repellent compositions impart hydrophobic properties to the nonporous substrate; whereas the antifog compositions impart hydrophilic properties to the nonporous substrate.
Therefore, it is an object of the present invention to provide an organopolysiloxane composition for applying to nonporous substrates. Another object of the present invention is to provide a transparent organopolysiloxane composition which may be applied to nonporous substrates to prevent fogging. A further object of this invention is to provide a transparent antifog composition which may be applied to nonporous substrates without causing streaking.